With no context on what caused you to go no-contact, nobody can give you a worth-a-shit answer.

Did he beat you, violently rape you, murder your mother, and rip off your pet birds head and shit in its corpse? You should definitely stay no-contact.

Did they make a mistake that anyone could make and you were just an angsty teenager that overreacted? You should probably talk to them.

Without the context of that interaction, don't take anyone's advice here.

I've been no contact for almost the same amount of time, so I'll tell you how I'd feel in the same boat.

My dad had no backbone to protect me while I was in his house, and he didn't bother trying to stay in my life after I left. He may not have done the abuse, but he definitely allowed it to happen due to inaction. I am always going to miss the parents I thought I had, but it won't add anything positive to my life to have contact again.

He is a stranger in a familiar coat

With absolutely zero context to what caused the rift initially -- I'll just say you only get one shot in this life, it's up to you to make it count. Most people would be heartbroken having zero contact with their children, it's entirely possibly he's decided enough is enough? Ultimately, is reconnecting going to negatively impact your life? If yes, simply ignore the attempt.

Maybe cut him some slack? A lot can happen in 20 years.

"More at the rest of the family"

If you're not mad at him that make that clear.

"Yo I'm NC with the family. Not mad at you and if you can STFU I'm willing to consider a discussion. But I'm doing this for you, not for me. What do you want?"

I lost my dad shortly after I got back in contact with him, and not trying to make up with him sooner is one of my greatest regrets. Obviously your situation may be different but it's probably worth giving him a second chance.

Listen to your you.

I went NC with my father when I was 13. About 10 years later we were in the same hospital room as his mom was getting ready to die. Then again a year later when his dad was, I asked the hospice nurse to remove him for my visit.

About 10 years after that I got a call from my step sis that my father was dying and likely wouldn't make it past a couple of days, that now was the time to come make amends.

I am so damn thankfull for that call. I still relish that I had the opportunity to actively say "No." Fuck that guy, worst human I've ever met. My life has been awesome without him.

"Fuck that" is perfectly valid. You don't owe them anything, and I think you should be extremely selfish in deciding whether to talk to them. You went no contact for a good reason.

Is there something you want to hear from them? E.g. "I'm sorry"
What would you want from the relationship?

IF you decide that you want a relationship, having clearly defined reasons for why you're doing it will help in assessing if you're getting what you want from it, and if you should continue the relationship.

YOU call the shots. YOU define the boundaries. There are no wrong answers.
Want to talk to him (and him only) on the phone for 20 minutes, once a year? Perfectly fine.
Happy birthday texts only? Valid.
You like no contact? No problem.

But now my dad wants to be real chummy and friendy with me? Fuck that, honestly

There's your answer, specially crafted by you, for you.

You can also tell the family that gave out your contact information without permission that since they have no concept of personal boundaries, you will not be taking any calls or visits from them, if you wish.

From what I read so far - I should say hello to him again.

When I split from my ex, who had become abusive, my second to oldest daughter said she wouldn't even go to his funeral if he died.

It's been ten years, and in the intervening time, he's quit drinking and become more reasonable, and she will talk to him occasionally.

So my question is, do you have reason to think he's changed? If not, I'd say change your phone number or block him. But people can change. If you think he's changed, then yes it might be good for both of you.

A lot of people get increasingly sentimental as they get older and the guy’s your dad. You don’t owe him anything and don’t have to engage at all, but he’d likely be grateful for even a surface level relationship with his estranged kid if you’re at all interested.

You might check around, see if anyone around him can vouch for him making major life changes.

It's really hard to know what to do. Both a changed dad who hopes to start new and an unchanged man who is just waiting for a chance to re-traumatize you would say similar things and be very friendly at first.

NC at 16 was rough probably.

One the one hand, you spent more time living apart or on your own than in contact with him, on the other hand, youth can be more impactful - so depending on your skills of emotion, trauma, processing etc. this can be good or difficult.

However you decide, you are somewhat strangers to each other now.

Do you think you and him could compartmentalise your relation and family?

When you miss someone, you will definitely get a chance to reconnect except if his/her is Dead

Well, think it over another time. I have no idea the circumstances that caused you to cut your family off so it depends. What would it take for you to see eye-to-eye with any particular family member once more? What would have to change from the other annoying members of your family before you even hear anything from them?

If you are willing, first see your father one-on-one, set your boundaries clearly and think about them beforehand, what you would be willing to be guilt-tripped into and what you are not, what behaviour is acceptable and what is not. You can keep it just to yourself and your father, and if any others come uninvited or crossed you again in ways you have directly clearly communicated you don't appreciate, then you can block them.